How to dynamically copy tables from information schema inside a trigger function - postgresql

Question

I have an insert trigger function in which NEW.schema_name references a schema. I want to dynamically copy the tables found inside that schema ('foobaz','barbaz') as 'foo' and 'bar'. I then can perform queries without dynamic sql.
How can I create a function or simply copy/paste the same block of code to achive that.
EDIT :
I cannot get that dynamic query to work.
The part inside the WITH statement is working.
Not the bottom 'execute' part. I do not know if it is a syntax problem, or bad cast or whatever constraint there is in pgsql that makes it not working.
WITH info_schema_subset_table as (SELECT table_schema, table_name,
array_to_string((regexp_split_to_array(table_name,'_'))[4:array_length(regexp_split_to_array(table_name,'_'),1)-1] as new_table
FROM information_schema.tables
where table_schema = "schema_searched"
ORDER BY new_table ASC)
EXECUTE 'CREATE TABLE $2 as (SELECT * FROM $1)'
USING info_schema_subset_table.table_schema || '.' ||info_schema_subset_table.table_name,info_schema_subset_table.new_table;
EDIT 2
... Broken code removed...
In the code below, in which I'm unsure if the syntax is right, I get the following from the trigger
Provider errors:
PostGIS error while adding features: ERREUR: l'opérateur n'existe pas : record ~~ unknown
LINE 1: SELECT old_table LIKE '%ens%'
^
HINT: Aucun opérateur ne correspond au nom donné et aux types d'arguments.
Vous devez ajouter des conversions explicites de type.
QUERY: SELECT old_table LIKE '%ens%'
CONTEXT: fonction PL/pgsql validation_sio.afi_validation_sio(), ligne 18 à CASE
EDIT 3 :
CREATE OR REPLACE FUNCTION foo.foo()
RETURNS TRIGGER AS
$BODY$
DECLARE
old_table record;
new_table record;
dynamic_query text;
BEGIN
IF TG_OP = 'INSERT'
THEN
FOR old_table IN SELECT table_schema|| '.' ||table_name
FROM information_schema.tables
where table_schema = NEW.nom_schema
LOOP
CASE
WHEN
old_table LIKE '%ens%' THEN
new_table := concat('SIT_',array_to_string((regexp_split_to_array(info_schema.old_table,'_'))[4:array_length(regexp_split_to_array(info_schema.old_table,'_'),1)-1],'_'));
ELSE
new_table := concat('SID_',array_to_string((regexp_split_to_array(info_schema.old_table,'_'))[4:array_length(regexp_split_to_array(info_schema.old_table,'_'),1)-1],'_'));
END CASE;
dynamic_query := format('SELECT * FROM' || old_table ||);
EXECUTE dynamic_query
INTO new_table;
END LOOP;
RETURN NEW;
END IF;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
CREATE TRIGGER foo
AFTER INSERT ON validation.validationfoo
FOR EACH ROW EXECUTE PROCEDURE foo.foo();

Answer 1

I've reformatted your trigger function a bit and changed a few things, see if this works.
CREATE OR REPLACE FUNCTION foo.foo()
RETURNS TRIGGER AS
$BODY$
DECLARE
old_table record;
new_table record;
dynamic_query text;
BEGIN
IF TG_OP = 'INSERT' THEN
FOR old_table IN
SELECT table_schema || '.' || table_name AS old_table_name
FROM information_schema.tables
WHERE table_schema = NEW.nom_schema
LOOP
new_table := concat(CASE WHEN old_table.old_table_name LIKE '%ens%' THEN 'SIT_' ELSE 'SID_' END,array_to_string((regexp_split_to_array(info_schema.old_table,'_'))[4:array_length(regexp_split_to_array(info_schema.old_table,'_'),1)-1],'_'));
dynamic_query := 'CREATE TABLE ' || new_table || ' AS SELECT * FROM ' || old_table.old_table_name;
EXECUTE dynamic_query;
END LOOP;
RETURN NEW;
END IF;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
So the main things:
old_table is a record, so your comparison of it to a string with LIKE was failing. You need to use the field name. So I gave your field a name, and used that field name in the LIKE comparison.
Changed the new_table assignment to put the CASE statement only on the one item that changes, to make the difference more obvious and the code more concise. Mind you, I don't know if the rest of that line is actually valid, I just left it as is.
Changed the creation dynamic_query. As I said in the comment, the format function was being used incorrectly, so I just went with standard string concatenation instead.
Changed dynamic_query's SQL to what I think you actually want it to do. You want it to copy the content of the table to a new table, right? So that will do it.

Answer 2

You cannot have EXECUTE inside an SQL statement, it is a PL/pgSQL statement.
Loop through the tables and issue one EXECUTE for each.
Mind that you cannot have a schema or table name as a parameter with USING, because these names need to be known at parse time.
Use the format function to construct your dynamic statement so you can avoid SQL injection by users who maliciously create tables with weird names.